The present invention generally relates to an apparatus for transforming a reciprocating axial movement of a pneumatic motor, a gas motor or a hydraulic motor of piston-cylinder type to a continuous rotary movement of one or more output shafts, and the invention is more particularly directed to an axial-to-rotary motor, in which there is used an endless drive belt extending over a first pulley which is fixed mounted in relation to the cylinder part of the pneumatic motor and over a second pulley which is mounted spaced from the piston rod, and in which the piston rod end of the reciprocatable motor is connected to a yoke having outer frames which enclose the two paths of the drive belt, and which includes a ratchet means which at the active expelling stroke of the piston provides a driving against one of the drive belt paths, and which at the retraction stroke of the piston provides a driving action against the second drive belt path, so that the drive belt, in both moving directions of the piston, will move in one and the same direction, and so that the shafts of the two pulleys will rotate in one and the same direction. A rotary drive movement thereby can be received, and taken out from one of the two shafts of the drive pulleys, or from both shafts.
An apparatus for transforming a reciprocating axial movement to a rotating movement, or vice versa, is known from the Swedish laid out publication No 433,393, which discloses an axial-to-rotary transforming apparatus, in which an endless cog belt is actuated by a reciprocatably moveable slide comprising a ratchet wheel having three ratchet segments provided at an angle of 120xc2x0 in relation to each other, and each comprising several cogs for co-operation with the cog belt and adapted to rotate a certain distance at each end position, whereby the cogs change contact from one cog belt path to the other cog belt, path.
The said known apparatus is disadvantageous in that the cog belt is moving at the moment when the ratchet wheel changes contact between the two cog belt paths, whereas the slide is still standing, and this leads to a non-desired play position of the rotary movement. The apparatus is also not formed for being used in combination with a pneumatic piston-cylinder apparatus.
In the present invention the driving is made from the shaft end of the axially reciprocatable motor, and it is the drive power from the cylinder that controls the changing operation while the piston rod is moving with maximum one cog difference. When the coupling means of the yoke has come to an engagement, the engagement force is controlled by the counter force, meaning the actual load on the output rotary shaft. This is done in that one or more ratchets of the coupling means clamps the drive belt against the inner surface of the yoke. The greater a force is needed the greater a force is applied between the ratchet and the yoke. Thanks to this structure it is possible to provide a fully acceptable function even when using a smooth or only slightly chamfered drive belt, for instance a reinforced drive belt having a rough surface, or even a conventional V-belt.
Thus, according to the invention the piston rod end of the reciprocatory motor is connected to a yoke which encloses the two paths of the drive belt, which yoke comprises two ratchet devices operating in opposite directions in relation to each other, and in which one of the ratchet devices, at the active expelling stroke of the piston, provides a clamping of the drive belt between said ratchet means and the inner surface of the yoke and thereby a driving of the drive belt corresponding to the active stroke of the reciprocatory motor, and in which the second ratchet device, at the return stroke of the piston, provides a driving against the second drive belt path, whereby the drive belt will move in one and the same direction at both piston movements, and whereby the two pulleys will rotate in one and the same direction.
In a preferred embodiment of the invention the inner surfaces of the yoke are formed with a friction increasing surface structure.
For eliminating the very little interruption of the driving of the drive belt which may appear during the change of actuation between the two drive belt paths, the apparatus according to the invention can be formed with two or more axial motors, which are mounted parallelly to each other, and which act on the same rotary shaft, and in which the yokes of the two or more apparatus are displaced in relation to each other by a little distance, corresponding to said interruption of the drive force, so that at least one of the drive belts always actuates the output rotary motor, and whereby any interruption of the driving is eliminated.
The drive apparatus can be formed as a twin arrangement comprising two parallely pneumatic cylinders, or two reciprocatable motors mounted opposed to each other. It is also possible to form the apparatus with several reciprocatable motors mounted in a star like arrangement. It is also possible to provide a gear reduction of the output rotary movement by interconnecting cog wheels of the output rotary shafts of two axial-to-rotary motors according to the invention using an interconnecting third cog wheel, preferably a surrounding cog wheel formed with inner cogs, whereby the rotary force can be received and taken out from one of the two primary shafts and/or from the common gear reduced secondary shaft.